modding 4.1 amplifier

[MD1032]

Aha! Brilliant idea. I'll try it sometime.

[MD1032]

Well today I put a 9 (wide) x 6 (deep) piece of eggcrate foam in my promedia 4.1 subwoofer. So far I like the results a lot.

That boominess and port noisey crap has to be at least cut in half. The bass sounds more like a tone now and less like a "fart". I would say the bass sounds like it has less punch, but this is probably because I'm used to the "fart" giving the bass a little extra oomph - granted, a terrible-sounding oomph. I have to turn up the bass a little more as it is a bit muted, but overall I'm extremely pleased with what I hear.

Taking apart the subwoofer was the easiest thing I have ever done in terms of taking big electronics apart. Unscrew the 8 screws, pop it out, and push in the foam. I actually cut an arc of foam away from each side, fearing the foam might come in contact with the woofers. At any rate, no melting smells yet or buzzing sounds, so I'm pretty sure it's OK. I'll take a sniff in the port later.

I doubt my parents would like me to find out I used their foam bed cushion thing to dampen my subwoofer, but then again, it's been sitting in the basement for years and they'll never notice!

I highly recommend trying this mod. I think at this point the lack of punch I described is a lack of upper bass, the result of the sattelite midbass drivers possibly being underpowered or just not being powerful enough themselves. I've noticed this before (listen to the high end of a bass guitar and compare it to the loudness of the low end...it's not balanced). Maybe it's time to build some cables.

Pictures, if you're interested:

http://photobucket.com/albums/y6/John9013/promedia41mod/

[craftsman]

I would suggest that you flip the foam around so that the fingers of the foam point upwards. You might find an improvement in the sound....

[rjon17469]

And glue it.

[Static]

Wow - what a great thread!

I've had my 4.1s for a couple of years, and I still love them. I was

wondering if PC speakers had improved a lot in the meantime, maybe my

old Klipsch set couldn't hold up to what was being sold today ... Nice

to know there are plenty of other people who still think they sound

great!

I definitely want to replace the speaker wire, and have started a

thread asking how to do that. Reading this thread has made me want to

try tweaking the sub too! Might have to ask for some advice on that as

well.

MD103 - Thanks for the link to your photos - I want to try something

like that and your page will definitely help! I did have a question

though - as far as the eggcrate foam goes, if you're using that to

dampen sound,

doesn't that mean it should be able to absorb sound? (Or do I

misunderstand what the term "dampening" means in this context?) Back

when I wanted to build acoustic panels for my home theater, I did a lot

of research, and I think I remember reading that eggcrate foam doesn't

absorb

sound too well. Your ears will make the final judgement, of course,

but that is what I remember reading. (I ended up making my panels out

of fiberglass and burlap and they are EXCELLENT at absorbing unwanted

reflections - the single best addition to my speaker setup I ever made.)

Lots of good info here. I hope this thread keeps going!

[craftsman]

A classic mistake is to believe that the new stuff is actually better. A good sounding speaker is a good sounding speaker. Of course, it is not to say that improvements can't be made....

If you do a search on the 'net about speakers and foam, you will find that most speakers work on the principle of eliminating the reflections of sound from inside of the speaker compartment to improve response and clarity of the sound. Getting some good quality accoustic foam is worth the trouble and besides it's not that expensive....

[craftsman]

As readers of this thread know, I've always been one to say "what's in the box can be improved".

Here's a run down on what I've done to my 4.1s:

1. Added decoupling caps to all of the op-amps I can find (both in the amp and the control pod).

2. Added additional caps to the CP-1.

3. Replaced the caps on the power supply section with larger caps.

4. Added sound dampening vinyl to the satelittes.

5. Added sound dampening foam to the sub.

6. Replaced the speaker wires with some 16 gauge stuff.

Here's what I fixed:

a. volume control staticy.

b. burnt resistors.

You may also know that the my amp on the 4.1s have stopped working (still have to fix that). However, I have recently purchased a 5.1 Ultra Sub and control unit from E-bay so I've been using that to drive my satelittes. Having my sats back, I decided to address something that has been bugging me - the crossover. Using eezip's web page - http://web.ics.purdue.edu/~shultzc/klipschxoverupgrade.htm - as a template, I replaced all of the components on the pcboard with most of the suggested components from http://www.partsexpress.com. I substituted the Mills 5.0 Ohm [005-5] unit for the Dayton one. Each Mills resistor was $2 more but what the hay - if I'm going to be replacing the parts I should be using the better ones!

So far, I modified one sat and I can say that I agree with eezip's observations - "I noticed a punchier mid especially in guitars. Vocals had less sibilance and were less fuzzy. The tweet was less crunchy and more detailed on hi hats. Basically, everything was a bit crisper and cleaner. " He stated that there wasn't a big difference but I would have to disagree (maybe it's the resistor...) - the difference is pretty big as I switch the balance between the modified one and the normal one. Each instrument is clearer and comes away from the background. As for vocals, much improved over the base - cleaner, and they stand out from the background.